This technical report consists of two papers discussing concurrency control facilities for multiuser software development environments. A Marvelous Extended Transaction Processing Model briefly sketches the previously developed commit-serializability model and then applies it to the MARVEL kernel for software development environments. A Participant Semantics for Serializable Transactions describes our first pass at a different extended transaction model that moves users inside the system, so certain users may participate in transactions and the interactions among transactions while all other users observe only a serial order for the transactions.